First Robot Car

So i am completely new to working with an Arduino or anything related to robotics. I am a software engineer as a day job and decided to try this out for a hobby!

So i purchased this kit https://www.sparkfun.com/products/10825 and I have everything setup and working. However, one of the motors is turning slightly slower than the other. I was wondering if this is a defect with one of the motors or is this something you have to account for sometimes? I know i could adjust the speed for the faster one to account for it but did not know if that is the correct solution.

Thank you for reading!

Likely there is some problem - could simply be some extra friction on one side (remember this is cheap plastic moulding, not a precision engineered part).

If you can swap the motors round but leave the rest of the mechanics in place that would identify if it was the motor or the gearing/wheels that is at fault.

Have you checked the motor by powering the motors directly from the same supply/battery pack?

Have you tried swapping the connections to the motor shield to tell if its that causing it?

Hi, I've used that Dagu chassis a few times and it is not unusual at all for that (or most dc-motor chassis) to have differences in motor speed with the same applied voltage.. at least enough to have a curve instead of perfectly straight movement.

If you want better control, you either need to use a rotation sensor and keep correcting for the difference and/or experiment with the correction factor in software.

Some robot chassis come with a slotted disc on each motor intended for closed-loop control. THAT will go straight...

MarkT thank you for the reply, i will try those suggestions tonight and report back.

terryking228 when you say "slotted disc" are they #4 in this PDF http://dlnmh9ip6v2uc.cloudfront.net/datasheets/Robotics/MagicianChassisInst.pdf they attach to the motor also but i didnt know what you actually use them for?

MarkT i tried switching the physical locations and tried swapping the connection on the motor shield and the same motor is always a little slower. Its barely noticeable to the eye but when it drives it always turns pretty aggressively to the right.